Extended audio bandwidths cause interference on adjacent channels. This is a major disadvantage compared to FM and digital modes where the demodulated audio is more objective. With AM, it largely depends on the frequency filters of each receiver how the audio is reproduced. In the UK, most stations use a bandwidth of 6.3 kHz. However, many stations use audio bandwidths up 10 kHz, which is not Hi-Fi but sufficient for casual listening. This is adequate for talk and news but not for high-fidelity music. The 9/10 kHz channel stepping on MW requires limiting the audio bandwidth to 4.5/5 kHz because the audio spectrum is transmitted twice on each side band. The range above 1610 kHz is primarily only used by low-power stations it is the preferred range for services with automated traffic, weather, and tourist information. North America uses 118 channels from 530–1700 kHz using 10 kHz spaced channels. Australia uses an expanded band up to 1701 kHz. The total allocated spectrum including the modulated audio ranges from 526.5–1606.5 kHz. Frequency coordination avoids the use of adjacent channels in one area. Spectrum and channel allocation areaįor Europe, Africa and Asia the MW band consists of 120 channels with carrier frequencies from 531–1602 kHz spaced every 9 kHz. The term is a historic one, dating from the early 20th century, when the radio spectrum was divided on the basis of the wavelength of the waves into long wave (LW), medium wave, and short wave (SW) radio bands. Many countries in Europe have switched off or limited their MW transmitters since the 2010s. In Europe, digital radio is gaining popularity and offers AM stations the chance to switch over if no frequency in the FM band is available, (however digital radio still has coverage issues in many parts of Europe). MW was the main radio band for broadcasting from the beginnings in the 1920s into the 1950s until FM with a better sound quality took over. Digital modes are possible but have not reached momentum yet. Strong transmitters cover larger areas than on the FM broadcast band but require more energy and longer antennas. In addition, amplitude modulation (AM) is often more prone to interference by various electronic devices, especially power supplies and computers. This can cause increased interference because on most channels multiple transmitters operate simultaneously worldwide. Improved signal propagation at night allows the reception of much longer distance signals (within a range of about 2,000 km or 1,200 miles). During the daytime, reception is usually limited to more local stations, though this is dependent on the signal conditions and quality of radio receiver used. The spectrum provides about 120 channels with more limited sound quality than FM stations on the FM broadcast band. Medium wave ( MW) is the part of the medium frequency (MF) radio band used mainly for AM radio broadcasting. In two words “absolute jack!” A double check of everything revealed nothing obvious.Typical mast radiator of a commercial medium wave AM broadcasting station, Chapel Hill, North Carolina, U.S. I plumbed up a Y-splitter on the audio out from my PC, hooked it to the decoder and loaded up a test MP3 file from the ARRL Morse Practice Archive and waited to see what happened! Application of a few stand off spacers on the Arduino helped with that. With all the shields stacked up the prototype was starting to resemble the leaning tower of Pisa and preventing it from toppling was a pain. It had counted 1837237 seconds since inception, which equates to 21.26 days. With a certain degree of regret I had to unplug my LCD shield which was occupying the only free USB port on my computer. So after an hours fiddly work soldering up the necessary links it was time to test this thing. In less than half an hour the below diagram which is missing from the book was emailed over by Jack (W8TEE) and Dennis (W6DQ). After several hours and a growing spider web of pencil on my circuit layout diagram I decided to wing it and emailed the authors directly, as the publishers’ support page was less than useless. I started working my way through the circuit schematic after a considerable amount of Google time looking for publishing errata, with zero success. There’s no help with wiring up the components on the prototyping shield. It was at this point I noticed there’s one all mighty faux pas in Arduino Projects for Amateur Radio. Here’s the partially completed shield prior to making all of the necessary wiring connections. So after playing with Asian QRP transceivers for the past few weeks/months it was time to get things back on track and crack on with all things CW & Morse.Īfter successfully building the LCD Shield portion of this project the next stage was the actual decoder shield.
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